1. FIELD of the Invention
The present invention relates to a platen for a thermal transfer printer.
2. Description of the Prior Art
A conventional platen of this type comprises a support, and a platen body made of an elastic material mounted on the support and having a low hardness (e.g., 20 to 50 as defined in a JIS A hardness test), as described in U.S. Patent 4,134,496.
The hardness of the platen body made of an elastic material is low due to the following reason. In a thermal transfer printer, tight contact between a thermal printing head and the platen body throughout the entire printing area in the widthwise direction is a necessary condition. If an elastic material having a high hardness is used, high precision for mounting the platen body in a printer housing must be assured. However, it is difficult to obtain such high mounting precision in practice. The hardness of the platen body is decreased to absorb mounting errors by utilizing elasticity of the platen body. More specifically, when the thermal printing head strikes the platen body, the platen body is flexed and assures tight contact with the thermal head surface. In other words, the thermal printing head can be brought into tight contact with a printing sheet through an ink ribbon so as to prevent printing errors such as transfer blinding and transfer omissions.
The conventional platen described above has the following disadvantage. Since the hardness of the platen body made of an elastic material is low, strong contact of the thermal head with the platen body does not increase a reaction force (i.e., a resistance of the platen body). In this state, tight contact between the thermal printing head and the platen body cannot be obtained. In a conventional printer having a conventional platen, only printing sheets having a Bekk smoothness of 100 sec or more can be used. Therefore, it is difficult to print information on rough surface paper with microindentations on its surface.